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Chronic pain after surgery
PREOPERATIVE ASSESSMENT
Chronic pain after surgery
that there are numerous factors affecting the incidence of persistent post-surgical pain. There is no doubt that chronic postsurgical pain is a significant problem worthy of attention. An estimate based on data available up to 2006 showed that the incidence of chronic pain after surgery was 10e50% and this was severe in 2e10%. Chronic pain is known to severely affect quality of life and has significant economic consequences. It has been estimated that even when using the lowest quoted figures there may be 41,000 new cases each year in the UK alone.1
Iain Jones Francoise Bari
Abstract Chronic pain after surgery is an area of considerable interest. Sufferers of chronic pain experience a poor quality of life, and the economic costs of treatment of the condition and resulting disability are high. Factors such as severe preoperative pain, psychosocial factors and particular surgical procedures have been identified as risk factors. Neuropathic mechanisms are involved in the pathophysiology of chronic post-surgical pain and our understanding of this continues to grow. Much interest has focussed on perioperative analgesic interventions to reduce the incidence and severity, however as yet the evidence is neither compelling nor consistent. At present there remains a need for education of the medical profession and the public of the risks of chronic post-surgical pain, so that unnecessary or inappropriate operations are minimized.
Pathophysiology The mechanisms of CPSP are complex and different mechanisms will be responsible for different pain syndromes even after the same operation. Tissue trauma, which is the inevitable consequence of surgery, results in inflammatory and immune reactions within tissues. This results in the release of neurotransmitters that act locally and in the spinal cord to produce hypersensitivity and ectopic neural activity, which contributes to central sensitization. Central sensitization occurs when repetitive nociceptive stimuli result in altered dorsal horn activity and amplification of sensory flow. These changes can lead to spontaneous and evoked symptoms associated with neuropathic pain; for example allodynia and hyperalgesia. Nerve injury during surgery has been implicated in the development of CPSP and whilst trauma to nerves is an important cause of persistent pain following surgery there is no simple relationship between nerve damage and chronic pain. For example, pain after thoracotomy is well recognized. Intraoperative damage to intercostal nerves is also well recognized, therefore this intercostal nerves damage had been postulated as a causative factor. However studies have not demonstrated an association between intercostal nerve damage assessed at the time of thoracotomy by nerve conduction studies and the development of pain 3 months later.2 Similarly, although damage to the intercostobrachial nerve has been implicated in the development of persistent pain following mastectomy, many patients with objective signs of nerve injury such as numbness do not develop chronic pain.3 It appears that merely avoiding the sectioning of major nerve trunks is not sufficient to prevent CPSP and sectioning nerves does not always result in chronic pain. It is not possible to perform operations without injuring elements of the nervous system at some level. A number of questions still exist as to what level of nerve injury is required to induce the changes that result in neuropathic pain. For example, can damage to tissues other than nerves cause neuropathic pain? And, what are the relative contributions of central and peripheral changes in the nervous system to the development of persistent pain following surgery?
Keywords Chronic; pain; prevention; risk factors; surgery
Introduction Definition of pain Pain is defined by the International Association for the Study of Pain (IASP) as an unpleasant sensory and emotional experience associated with actual or potential damage or described in terms of tissue damage. There has been a lack of an accepted definition for chronic post-surgical pain (CPSP) which has been a barrier in interpreting the literature and is a major reason for the wide variation in the published incidence of chronic post-surgical pain. However it has been suggested that chronic post-surgical pain should be defined according to the following criteria: the pain should have developed after a surgical procedure the pain should be of at least 2 months’ duration other causes should have been excluded, for example continuing infection, continuing malignancy (after cancer surgery) or chronic infection the possibility that the pain is continuing from a preexisting problem.1
Incidence The incidence of CPSP varies between procedures and between studies. Table 1 shows the approximate incidence after common procedures. There is some variance between studies which may be attributed to differences in trial design and also the likelihood
Risk factors (Boxes 1 and 2) Iain Jones MB ChB FRCA FFPMRCA is a Consultant in Anaesthesia and Pain Management at the Royal Victoria Infirmary, Newcastle Upon Tyne, UK. Conflicts of interest: none.
Risk factors can be broadly grouped into patient factors and medical factors.
Francoise Bari BSc(Hons) MSc MB ChB(Hons) FRCA is a Specialty Registrar in Anaesthesia and Intensive Care at the Royal Victoria Infirmary, Newcastle Upon Tyne, UK. Conflicts of interest: none.
In breast and hernia repair, increasing age seems to reduce the risk of chronic pain. A review revealed that chronic pain after breast surgery was more likely in younger patients but the
SURGERY 32:2
Age
93
Ó 2014 Elsevier Ltd. All rights reserved.
PREOPERATIVE ASSESSMENT
Incidence of chronic post-surgical pain after common procedures Type of operation
Criteria for chronic post-surgical pain C
Incidence of chronic pain (%)
C
Mastectomy Caesarean section Amputation Cardiac surgery Hernia repair Cholecystectomy Hip replacement Thoracotomy
20e50 6 50e85 30e55 5e35 5e50 12 5e65
C C
Pain developing after a surgical procedure Pain for at least 2 months Other causes of pain excluded (e.g. malignancy, infection) Pain continuing from a pre-existing pain problem excluded
Box 2
shown to be strongly related to enhanced pain sensitivity in both healthy adults and patients with chronic pain. Several studies of women undergoing breast surgery have identified an association between catastrophizing and persistent post-surgical pain.6 Whilst it is acknowledged that psychosocial factors play an important role in the genesis of persistent postoperative pain, more work is required to elucidate their precise nature and influence and how to negate them.
Macrae et al., 2008.
Table 1
disease in this group was more severe and invasive which may account for some of the difference in incidence of chronic pain with age. The probability of developing chronic pain after breast cancer surgery was found to reduce by 5% with each year of increasing age.1,4
Genetic factors There is growing interest in the concept of genetic variability accounting for some of the variability in response to painful stimuli including surgery. Some rare pain syndromes associated with insensitivity to pain are thought to be caused by abnormalities in the voltage-gated sodium channel Na(v)1.7 and variations have been found in response to endogenous and therapeutic opioids which have been linked to variations of the mu-opioid and catecholamine-o-methyltransferase genes.5 There is work from experimental studies on mice that show genetic factors influence whether mice develop neuropathic pain following nerve injury.1 Furthermore it is suspected that there are certain conditions which may be markers for developing chronic pain after an injury. These conditions include fibromyalgia, migraine and irritable bowel syndrome. In a study of women with pain after hysterectomy those with pain problems elsewhere than in the pelvis before surgery had an increased risk of chronic post-surgical pain. The most common areas were the head, neck, shoulders and low back, which is similar to the areas frequently associated with pain in fibromyalgia.1 This suggests there may be an underlying vulnerability to developing persistent pain for which there may be a genetic basis.
Psychosocial factors It is well recognized that psychosocial factors play a significant role in the development and maintenance of chronic pain and also the disability associated with it. Indeed psychological approaches such as cognitive behavioural therapy have been used widely in the management of chronic pain. Psychological factors have been found to correlate with poor outcome following spinal surgery. A 2001 review of this topic identified an association between poor outcome with preoperative pain sensitivity, depression, anger, anxiety and poor pain coping strategies.5 Further studies have identified factors such as anxiety, depression, sleep disturbance and catastrophizing (having exaggerated negative beliefs and responses) to be important contributors to the development of persistent post-surgical pain. When measured prospectively these predict the trajectory of acute pain or analgesic consumption after breast cancer surgery and in other settings also predict the development of chronic orofacial pain and widespread pain. Catastrophizing has been
Preoperative pain
Factors associated with increased likelihood of chronic postoperative pain C C C C C
C
The severity of preoperative pain has been shown in many studies to correlate with the development of persistent post-surgical pain. This was first noted in the observations of patients developing phantom pain after amputation, and associations have also been reported with other common procedures such as hernia repair and thoracotomy. Interestingly pain after hip arthroplasty has not been found to correlate with pain afterwards.5
Severity of preoperative pain Nerve injury Psychosocial factors Severity of immediate postoperative pain Specific surgical procedures, e.g. mastectomy, thoracotomy, amputation Extent of surgery
Acute postoperative pain Many studies have shown a correlation between the severity of acute postoperative pain and the development of persistent pain. This has been identified as a risk factor for pain following
Box 1
SURGERY 32:2
94
Ó 2014 Elsevier Ltd. All rights reserved.
PREOPERATIVE ASSESSMENT
hernia surgery, breast cancer surgery, total hip replacement and Caesarean section.1
The effect of anti-convulsants such as gabapentin and pregabalin, and anti-depressants such as venlafaxine on early postoperative pain has also been assessed widely and most data show an improvement in analgesia, a reduction in opioid requirement or both. However studies looking at longer-term outcome on persistent pain have been small and not showed an improvement.12 Despite the conflicting evidence it remains a reasonable hope that a multimodal approach reliably delivered and tailored to the needs of individual operations will eventually reduce the incidence of persistent post-surgical pain.
Surgical factors The size of operation does not show a simple correlation with CPSP. The type of operation (e.g. breast surgery, hernia repair and thoracotomy) and how it is performed influences the incidence of CPSP. Studies have found more chronic pain and poorer outcomes in general for operations lasting more than 3 hours. This may reflect serious pathology, complications or other health problems affecting complexity of the operation and outcome.7 In the case of chronic pain following mastectomy, surgical factors including more extensive surgery (total vs. partial mastectomy), axillary node dissection and reconstruction have been postulated to serve as important risk factors for chronic pain, but many studies do not support this association. Adjuvant treatment such as radiotherapy, chemotherapy and hormone therapy have also occasionally been associated with persistent pain.6 For hernia surgery there appears to be no correlation between CPSP and different types of open repair, but there does appear to be less pain after laparoscopic repair. The reduction in chronic pain after laparoscopic surgery has been confirmed by two systematic reviews. In addition, open cholecystectomy has a higher incidence of PSP than laparoscopic cholecystectomy.8 Whether the condition for which the operation was performed influences the incidence of chronic pain is controversial. For lower limb amputation, the reason for the amputation does not affect the incidence of chronic pain afterwards.9 In the case of surgery for hernias in the groin, the type of hernia does not seem to influence the prevalence of chronic pain, but whether surgery for recurrent hernias carries a risk is controversial.
Prevention As post-surgical pain syndromes are usually hard to treat, prevention is important. At present there is limited evidence for effective strategies, however two strategies are obvious.
Effective management of postoperative pain There is strong evidence that severe postoperative pain is associated with a high incidence of CPSP. It seems likely that some patients are more vulnerable to both acute postoperative pain and CPSP. However given the limitations in our understanding and ability to predict who is at risk, good pain control remains an important and achievable goal of peri-operative care. In many cases this stills remains a challenge. Reasons can be due to a systematic failure to implement changes into routine care, which may be due to a variety of reasons including lack of resources, technical problems, conflicting interests and organizational and cultural barriers.
Surgery as a risk factor Undergoing surgery remains an obvious risk factor for the development of persistent post-surgical pain. Strategies which could potentially reduce the requirements for surgery include public health measures to reduce risk factors for vascular disease such as smoking cessation and improved medical control of diabetes for which disease complications can require surgical intervention including amputation. Also improved screening programs and earlier diagnosis of conditions such as breast cancer may result in less invasive surgery with less postoperative morbidity. The risk of what is potentially a life-changing complication as a result of surgery should be born in mind when considering the need or appropriateness of a surgical procedure. The European Hernia Society guidelines no longer recommend surgery in asymptomatic or minimally symptomatic patients due to the risk of developing chronic pain and the low risk of incarceration. In this situation watchful waiting has been shown to be a safe strategy.13 Awareness of the risk of chronic pain is particularly relevant when patients wish to have surgery for reasons other than illness or disability, for example male and female sterilization and some cosmetic operations, which may be performed for aesthetic rather than medical reasons. Chronic pain after vasectomy has been the subject of several studies which have shown an incidence of chronic pain of around 15%.14 Reports of studies of breast augmentation surgery have reported incidences of pain varying between 21% and 50% depending on the type of operation and up to 22% after breast reduction surgery.15 Cosmetic surgery is widely advertised and easily
Anaesthesia and analgesia From our understanding of the pathophysiology of pain, it is believed that tissue trauma as a consequence of surgery sensitizes the nervous system and that this hypersensitized state contributes to the development of chronic pain. It therefore seems sensible to try and reduce the nociceptive input to the spinal cord during and after the operation. Local anaesthetic procedures improve immediate postoperative pain relief and there has been interest as to whether they can reduce persistent pain. A study assessing the effect of paravertebral block on immediate postoperative pain after mastectomy by assessing pain 1 year after surgery found that both the incidence of chronic pain (43% vs 77%) and its intensity was less in those who had received pre-operative paravertebral block with local anaesthetic.10 There have also been studies showing benefit from local anaesthetic techniques in reducing persistent pain after hysterectomy, Caesarean section, iliac bone harvesting and thoracotomy; however other studies have not supported these conclusions.1 At one time it was thought that delivering pre-emptive regional analgesia would reduce post-operative problems such as phantom pain and there was considerable interest when some studies suggested that pre-emptive epidural analgesia might reduce the incidence of chronic phantom limb pain. However, later studies failed to replicate these early findings.5,11
SURGERY 32:2
95
Ó 2014 Elsevier Ltd. All rights reserved.
PREOPERATIVE ASSESSMENT
2 Maguire MF, Latter JA, Beggs R. A study exploring the role of intercostal nerve damage in chronic pain after thoracic surgery. Eur J Cardiothorac Surg 2006; 29: 873e9. 3 Ivens D, Hoe AL, Podd TJ. Assessment of morbidity from complete axilliary dissection. Br J Cancer 1992; 66: 136e8. 4 Poleshuck EL, Kacz J, Andrus CH, et al. Risk factors for chronic pain following breast surgery: a prospective study. J Pain 2006; 7: 626e34. 5 Niraj G, Rowbotham DJ. Persistent postoperative pain: where are we now? Br J Anaesthesia 2011; 107: 25e9. 6 Schreiber KL, Martel M, Schnol H. Persistent pain in postmastectomy patients: comparison of psychosocial characteristics between patients with and without pain. Pain 2013; 154: 660e8. 7 Peters ML, Sommer M, de Rijke, et al. Somatic and psychological predictors of long-term unfavourable outcome after surgical intervention. Ann Surg 2007; 245: 487e94. 8 Aasvang E, Kehlet H. Chronic postoperative pain: the case of inguinal herniorrhaphy. Br J Anaesthesia 2005; 95: 69e76. 9 Jensen TS, Krebs B, Nielson J, Rasmussen P. Immediate and long-term phantom limb pain in amputees: incidence clinical characteristics and relationship to pre-amputation limb pain. Pain 1985; 21: 267e8. 10 Kairaluoma PM, Bachmann MS, Rosenberg PH, Pere PJ. Preincisional paravertebral block reduces the prevalence of chronic pain after breast surgery. Anaest Analg 2006; 103: 703e8. 11 Ypsilantis E, Tnag TY. Pre-emptive analgesia for peripheral vascular disease: a systematic review. Ann Vasc Surg 2010; 24: 1139e46. 12 Amr YM, Yousef AAAM. Evaluation of efficacy of the peri-operative administration of Venlafaxine or Gabapentin on acute and chronic postmastectomy pain. Clin J Pain 2010; 26: 381e5. 13 Simons MP, Aufenacker T, Miserez M. European Hernia Society Guidelines on the treatment of inguinal hernia in adult patients. Hernia 2009; 13: 343e403. 14 Leslie TA, Illing RO, Cranston DW, Guillebaud J. The incidence of chronic scrotal pain after vasectomy: a prospective audit. BJU Int 2007; 100: 1300e3. 15 Wallace MS, Wallace AM, Lee J, Dobke MK. Pain after breast surgery: a survey of 282 women. Pain 1996; 66: 195e205.
available but most organizations offering breast augmentation and reduction operations do not mention chronic pain as a complication.
Conclusion Chronic pain after surgery is a relatively common problem affecting thousands of patients each year in the UK. The likelihood of persistent pain after some types of surgery should be a factor in the risk benefit analysis and as such, part of an informed consent procedure, before proceeding to surgery. Prevention is key to the problem but unfortunately we have made little progress in this area as yet. A number of approaches currently available have been examined and although a few studies have shown benefit the effect is often small, and evidence is not consistent. As far as clinical practice is concerned the severity of postoperative pain has been recognized as a predictive factor for persistent pain in many studies. Excellent techniques are available to address this and it may be worth concentrating attention on those patients who are in severe pain after surgery. Much work remains to be done particularly in the fields of mechanisms and risk factors. Ensuring optimal management of acute post-operative pain is a strategy, which may prevent CPSP, but there are often organizational and cultural barriers to overcome in order to achieve improvement. There is also a need for education of the medical profession and general public about the problem. If patients and their doctors are aware of the risks it might deter some patients from undergoing inappropriate and unnecessary operations and thereby reduce the risk and incidence of chronic post-surgical pain. A
REFERENCES 1 Macrae W. Chronic post surgical pain 10 years on. Br J Anaesthesia 2008; 101: 77e86.
SURGERY 32:2
96
Ó 2014 Elsevier Ltd. All rights reserved.
Chronic pain after surgery
that there are numerous factors affecting the incidence of persistent post-surgical pain. There is no doubt that chronic postsurgical pain is a significant problem worthy of attention. An estimate based on data available up to 2006 showed that the incidence of chronic pain after surgery was 10e50% and this was severe in 2e10%. Chronic pain is known to severely affect quality of life and has significant economic consequences. It has been estimated that even when using the lowest quoted figures there may be 41,000 new cases each year in the UK alone.1
Iain Jones Francoise Bari
Abstract Chronic pain after surgery is an area of considerable interest. Sufferers of chronic pain experience a poor quality of life, and the economic costs of treatment of the condition and resulting disability are high. Factors such as severe preoperative pain, psychosocial factors and particular surgical procedures have been identified as risk factors. Neuropathic mechanisms are involved in the pathophysiology of chronic post-surgical pain and our understanding of this continues to grow. Much interest has focussed on perioperative analgesic interventions to reduce the incidence and severity, however as yet the evidence is neither compelling nor consistent. At present there remains a need for education of the medical profession and the public of the risks of chronic post-surgical pain, so that unnecessary or inappropriate operations are minimized.
Pathophysiology The mechanisms of CPSP are complex and different mechanisms will be responsible for different pain syndromes even after the same operation. Tissue trauma, which is the inevitable consequence of surgery, results in inflammatory and immune reactions within tissues. This results in the release of neurotransmitters that act locally and in the spinal cord to produce hypersensitivity and ectopic neural activity, which contributes to central sensitization. Central sensitization occurs when repetitive nociceptive stimuli result in altered dorsal horn activity and amplification of sensory flow. These changes can lead to spontaneous and evoked symptoms associated with neuropathic pain; for example allodynia and hyperalgesia. Nerve injury during surgery has been implicated in the development of CPSP and whilst trauma to nerves is an important cause of persistent pain following surgery there is no simple relationship between nerve damage and chronic pain. For example, pain after thoracotomy is well recognized. Intraoperative damage to intercostal nerves is also well recognized, therefore this intercostal nerves damage had been postulated as a causative factor. However studies have not demonstrated an association between intercostal nerve damage assessed at the time of thoracotomy by nerve conduction studies and the development of pain 3 months later.2 Similarly, although damage to the intercostobrachial nerve has been implicated in the development of persistent pain following mastectomy, many patients with objective signs of nerve injury such as numbness do not develop chronic pain.3 It appears that merely avoiding the sectioning of major nerve trunks is not sufficient to prevent CPSP and sectioning nerves does not always result in chronic pain. It is not possible to perform operations without injuring elements of the nervous system at some level. A number of questions still exist as to what level of nerve injury is required to induce the changes that result in neuropathic pain. For example, can damage to tissues other than nerves cause neuropathic pain? And, what are the relative contributions of central and peripheral changes in the nervous system to the development of persistent pain following surgery?
Keywords Chronic; pain; prevention; risk factors; surgery
Introduction Definition of pain Pain is defined by the International Association for the Study of Pain (IASP) as an unpleasant sensory and emotional experience associated with actual or potential damage or described in terms of tissue damage. There has been a lack of an accepted definition for chronic post-surgical pain (CPSP) which has been a barrier in interpreting the literature and is a major reason for the wide variation in the published incidence of chronic post-surgical pain. However it has been suggested that chronic post-surgical pain should be defined according to the following criteria: the pain should have developed after a surgical procedure the pain should be of at least 2 months’ duration other causes should have been excluded, for example continuing infection, continuing malignancy (after cancer surgery) or chronic infection the possibility that the pain is continuing from a preexisting problem.1
Incidence The incidence of CPSP varies between procedures and between studies. Table 1 shows the approximate incidence after common procedures. There is some variance between studies which may be attributed to differences in trial design and also the likelihood
Risk factors (Boxes 1 and 2) Iain Jones MB ChB FRCA FFPMRCA is a Consultant in Anaesthesia and Pain Management at the Royal Victoria Infirmary, Newcastle Upon Tyne, UK. Conflicts of interest: none.
Risk factors can be broadly grouped into patient factors and medical factors.
Francoise Bari BSc(Hons) MSc MB ChB(Hons) FRCA is a Specialty Registrar in Anaesthesia and Intensive Care at the Royal Victoria Infirmary, Newcastle Upon Tyne, UK. Conflicts of interest: none.
In breast and hernia repair, increasing age seems to reduce the risk of chronic pain. A review revealed that chronic pain after breast surgery was more likely in younger patients but the
SURGERY 32:2
Age
93
Ó 2014 Elsevier Ltd. All rights reserved.
PREOPERATIVE ASSESSMENT
Incidence of chronic post-surgical pain after common procedures Type of operation
Criteria for chronic post-surgical pain C
Incidence of chronic pain (%)
C
Mastectomy Caesarean section Amputation Cardiac surgery Hernia repair Cholecystectomy Hip replacement Thoracotomy
20e50 6 50e85 30e55 5e35 5e50 12 5e65
C C
Pain developing after a surgical procedure Pain for at least 2 months Other causes of pain excluded (e.g. malignancy, infection) Pain continuing from a pre-existing pain problem excluded
Box 2
shown to be strongly related to enhanced pain sensitivity in both healthy adults and patients with chronic pain. Several studies of women undergoing breast surgery have identified an association between catastrophizing and persistent post-surgical pain.6 Whilst it is acknowledged that psychosocial factors play an important role in the genesis of persistent postoperative pain, more work is required to elucidate their precise nature and influence and how to negate them.
Macrae et al., 2008.
Table 1
disease in this group was more severe and invasive which may account for some of the difference in incidence of chronic pain with age. The probability of developing chronic pain after breast cancer surgery was found to reduce by 5% with each year of increasing age.1,4
Genetic factors There is growing interest in the concept of genetic variability accounting for some of the variability in response to painful stimuli including surgery. Some rare pain syndromes associated with insensitivity to pain are thought to be caused by abnormalities in the voltage-gated sodium channel Na(v)1.7 and variations have been found in response to endogenous and therapeutic opioids which have been linked to variations of the mu-opioid and catecholamine-o-methyltransferase genes.5 There is work from experimental studies on mice that show genetic factors influence whether mice develop neuropathic pain following nerve injury.1 Furthermore it is suspected that there are certain conditions which may be markers for developing chronic pain after an injury. These conditions include fibromyalgia, migraine and irritable bowel syndrome. In a study of women with pain after hysterectomy those with pain problems elsewhere than in the pelvis before surgery had an increased risk of chronic post-surgical pain. The most common areas were the head, neck, shoulders and low back, which is similar to the areas frequently associated with pain in fibromyalgia.1 This suggests there may be an underlying vulnerability to developing persistent pain for which there may be a genetic basis.
Psychosocial factors It is well recognized that psychosocial factors play a significant role in the development and maintenance of chronic pain and also the disability associated with it. Indeed psychological approaches such as cognitive behavioural therapy have been used widely in the management of chronic pain. Psychological factors have been found to correlate with poor outcome following spinal surgery. A 2001 review of this topic identified an association between poor outcome with preoperative pain sensitivity, depression, anger, anxiety and poor pain coping strategies.5 Further studies have identified factors such as anxiety, depression, sleep disturbance and catastrophizing (having exaggerated negative beliefs and responses) to be important contributors to the development of persistent post-surgical pain. When measured prospectively these predict the trajectory of acute pain or analgesic consumption after breast cancer surgery and in other settings also predict the development of chronic orofacial pain and widespread pain. Catastrophizing has been
Preoperative pain
Factors associated with increased likelihood of chronic postoperative pain C C C C C
C
The severity of preoperative pain has been shown in many studies to correlate with the development of persistent post-surgical pain. This was first noted in the observations of patients developing phantom pain after amputation, and associations have also been reported with other common procedures such as hernia repair and thoracotomy. Interestingly pain after hip arthroplasty has not been found to correlate with pain afterwards.5
Severity of preoperative pain Nerve injury Psychosocial factors Severity of immediate postoperative pain Specific surgical procedures, e.g. mastectomy, thoracotomy, amputation Extent of surgery
Acute postoperative pain Many studies have shown a correlation between the severity of acute postoperative pain and the development of persistent pain. This has been identified as a risk factor for pain following
Box 1
SURGERY 32:2
94
Ó 2014 Elsevier Ltd. All rights reserved.
PREOPERATIVE ASSESSMENT
hernia surgery, breast cancer surgery, total hip replacement and Caesarean section.1
The effect of anti-convulsants such as gabapentin and pregabalin, and anti-depressants such as venlafaxine on early postoperative pain has also been assessed widely and most data show an improvement in analgesia, a reduction in opioid requirement or both. However studies looking at longer-term outcome on persistent pain have been small and not showed an improvement.12 Despite the conflicting evidence it remains a reasonable hope that a multimodal approach reliably delivered and tailored to the needs of individual operations will eventually reduce the incidence of persistent post-surgical pain.
Surgical factors The size of operation does not show a simple correlation with CPSP. The type of operation (e.g. breast surgery, hernia repair and thoracotomy) and how it is performed influences the incidence of CPSP. Studies have found more chronic pain and poorer outcomes in general for operations lasting more than 3 hours. This may reflect serious pathology, complications or other health problems affecting complexity of the operation and outcome.7 In the case of chronic pain following mastectomy, surgical factors including more extensive surgery (total vs. partial mastectomy), axillary node dissection and reconstruction have been postulated to serve as important risk factors for chronic pain, but many studies do not support this association. Adjuvant treatment such as radiotherapy, chemotherapy and hormone therapy have also occasionally been associated with persistent pain.6 For hernia surgery there appears to be no correlation between CPSP and different types of open repair, but there does appear to be less pain after laparoscopic repair. The reduction in chronic pain after laparoscopic surgery has been confirmed by two systematic reviews. In addition, open cholecystectomy has a higher incidence of PSP than laparoscopic cholecystectomy.8 Whether the condition for which the operation was performed influences the incidence of chronic pain is controversial. For lower limb amputation, the reason for the amputation does not affect the incidence of chronic pain afterwards.9 In the case of surgery for hernias in the groin, the type of hernia does not seem to influence the prevalence of chronic pain, but whether surgery for recurrent hernias carries a risk is controversial.
Prevention As post-surgical pain syndromes are usually hard to treat, prevention is important. At present there is limited evidence for effective strategies, however two strategies are obvious.
Effective management of postoperative pain There is strong evidence that severe postoperative pain is associated with a high incidence of CPSP. It seems likely that some patients are more vulnerable to both acute postoperative pain and CPSP. However given the limitations in our understanding and ability to predict who is at risk, good pain control remains an important and achievable goal of peri-operative care. In many cases this stills remains a challenge. Reasons can be due to a systematic failure to implement changes into routine care, which may be due to a variety of reasons including lack of resources, technical problems, conflicting interests and organizational and cultural barriers.
Surgery as a risk factor Undergoing surgery remains an obvious risk factor for the development of persistent post-surgical pain. Strategies which could potentially reduce the requirements for surgery include public health measures to reduce risk factors for vascular disease such as smoking cessation and improved medical control of diabetes for which disease complications can require surgical intervention including amputation. Also improved screening programs and earlier diagnosis of conditions such as breast cancer may result in less invasive surgery with less postoperative morbidity. The risk of what is potentially a life-changing complication as a result of surgery should be born in mind when considering the need or appropriateness of a surgical procedure. The European Hernia Society guidelines no longer recommend surgery in asymptomatic or minimally symptomatic patients due to the risk of developing chronic pain and the low risk of incarceration. In this situation watchful waiting has been shown to be a safe strategy.13 Awareness of the risk of chronic pain is particularly relevant when patients wish to have surgery for reasons other than illness or disability, for example male and female sterilization and some cosmetic operations, which may be performed for aesthetic rather than medical reasons. Chronic pain after vasectomy has been the subject of several studies which have shown an incidence of chronic pain of around 15%.14 Reports of studies of breast augmentation surgery have reported incidences of pain varying between 21% and 50% depending on the type of operation and up to 22% after breast reduction surgery.15 Cosmetic surgery is widely advertised and easily
Anaesthesia and analgesia From our understanding of the pathophysiology of pain, it is believed that tissue trauma as a consequence of surgery sensitizes the nervous system and that this hypersensitized state contributes to the development of chronic pain. It therefore seems sensible to try and reduce the nociceptive input to the spinal cord during and after the operation. Local anaesthetic procedures improve immediate postoperative pain relief and there has been interest as to whether they can reduce persistent pain. A study assessing the effect of paravertebral block on immediate postoperative pain after mastectomy by assessing pain 1 year after surgery found that both the incidence of chronic pain (43% vs 77%) and its intensity was less in those who had received pre-operative paravertebral block with local anaesthetic.10 There have also been studies showing benefit from local anaesthetic techniques in reducing persistent pain after hysterectomy, Caesarean section, iliac bone harvesting and thoracotomy; however other studies have not supported these conclusions.1 At one time it was thought that delivering pre-emptive regional analgesia would reduce post-operative problems such as phantom pain and there was considerable interest when some studies suggested that pre-emptive epidural analgesia might reduce the incidence of chronic phantom limb pain. However, later studies failed to replicate these early findings.5,11
SURGERY 32:2
95
Ó 2014 Elsevier Ltd. All rights reserved.
PREOPERATIVE ASSESSMENT
2 Maguire MF, Latter JA, Beggs R. A study exploring the role of intercostal nerve damage in chronic pain after thoracic surgery. Eur J Cardiothorac Surg 2006; 29: 873e9. 3 Ivens D, Hoe AL, Podd TJ. Assessment of morbidity from complete axilliary dissection. Br J Cancer 1992; 66: 136e8. 4 Poleshuck EL, Kacz J, Andrus CH, et al. Risk factors for chronic pain following breast surgery: a prospective study. J Pain 2006; 7: 626e34. 5 Niraj G, Rowbotham DJ. Persistent postoperative pain: where are we now? Br J Anaesthesia 2011; 107: 25e9. 6 Schreiber KL, Martel M, Schnol H. Persistent pain in postmastectomy patients: comparison of psychosocial characteristics between patients with and without pain. Pain 2013; 154: 660e8. 7 Peters ML, Sommer M, de Rijke, et al. Somatic and psychological predictors of long-term unfavourable outcome after surgical intervention. Ann Surg 2007; 245: 487e94. 8 Aasvang E, Kehlet H. Chronic postoperative pain: the case of inguinal herniorrhaphy. Br J Anaesthesia 2005; 95: 69e76. 9 Jensen TS, Krebs B, Nielson J, Rasmussen P. Immediate and long-term phantom limb pain in amputees: incidence clinical characteristics and relationship to pre-amputation limb pain. Pain 1985; 21: 267e8. 10 Kairaluoma PM, Bachmann MS, Rosenberg PH, Pere PJ. Preincisional paravertebral block reduces the prevalence of chronic pain after breast surgery. Anaest Analg 2006; 103: 703e8. 11 Ypsilantis E, Tnag TY. Pre-emptive analgesia for peripheral vascular disease: a systematic review. Ann Vasc Surg 2010; 24: 1139e46. 12 Amr YM, Yousef AAAM. Evaluation of efficacy of the peri-operative administration of Venlafaxine or Gabapentin on acute and chronic postmastectomy pain. Clin J Pain 2010; 26: 381e5. 13 Simons MP, Aufenacker T, Miserez M. European Hernia Society Guidelines on the treatment of inguinal hernia in adult patients. Hernia 2009; 13: 343e403. 14 Leslie TA, Illing RO, Cranston DW, Guillebaud J. The incidence of chronic scrotal pain after vasectomy: a prospective audit. BJU Int 2007; 100: 1300e3. 15 Wallace MS, Wallace AM, Lee J, Dobke MK. Pain after breast surgery: a survey of 282 women. Pain 1996; 66: 195e205.
available but most organizations offering breast augmentation and reduction operations do not mention chronic pain as a complication.
Conclusion Chronic pain after surgery is a relatively common problem affecting thousands of patients each year in the UK. The likelihood of persistent pain after some types of surgery should be a factor in the risk benefit analysis and as such, part of an informed consent procedure, before proceeding to surgery. Prevention is key to the problem but unfortunately we have made little progress in this area as yet. A number of approaches currently available have been examined and although a few studies have shown benefit the effect is often small, and evidence is not consistent. As far as clinical practice is concerned the severity of postoperative pain has been recognized as a predictive factor for persistent pain in many studies. Excellent techniques are available to address this and it may be worth concentrating attention on those patients who are in severe pain after surgery. Much work remains to be done particularly in the fields of mechanisms and risk factors. Ensuring optimal management of acute post-operative pain is a strategy, which may prevent CPSP, but there are often organizational and cultural barriers to overcome in order to achieve improvement. There is also a need for education of the medical profession and general public about the problem. If patients and their doctors are aware of the risks it might deter some patients from undergoing inappropriate and unnecessary operations and thereby reduce the risk and incidence of chronic post-surgical pain. A
REFERENCES 1 Macrae W. Chronic post surgical pain 10 years on. Br J Anaesthesia 2008; 101: 77e86.
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